Generally, waste management dewatering systems separate solids and fine particles from the liquid phase of drilling fluid, thereby leaving a clarified aqueous solution. In a drilling operation, dewatering allows the cleaning of waste fluids, such as, drilling fluids mixed with water from the rotary table, mud tanks, mud pumps, generators and from any other discharge point around a drilling rig. Typically, dewatering waste management systems clean drilling fluid through coagulation, flocculation, and/or mechanical separation.
Coagulation occurs when the electrostatic charge on a solid is reduced, destabilizing the solid and allowing it to be attracted to other solids by van der Waals forces. Flocculation is the binding of individual solid particles into aggregates of multiple particles. Flocculation is physical, rather than electrical, and occurs when one segment of a flocculating polymer chain absorbs simultaneously onto more than one particle. Mechanical separation includes mechanical devices (e.g., hydrocyclones and centrifuges) that remove solid particles from a solution.
Traditionally, methods for removing solids from solutions in the dewatering of drilling fluid included the replication of the natural mud flocculation mechanisms using either calcium or chlorine based ion contamination. Lime and various chloride sources (e.g., AlCl3) were used for flocculation. The solid aggregates could then be separated out by gravity filtration and/or a mechanical device, as described above. However, with the introduction of non-dispersed, inhibitive water-based drilling fluids (e.g., partially-hydrolyzed polyacrylamide and KCl), the clay particles within a mud system were already conditioned to resist ion contamination (i.e., resistant to flocculation and/or aggregation). Thus, the dewatering of water-base drilling fluids require multi-charge, high molecular weight polymers for flocculation.
Typically, polymers used for flocculation are manufactured in dry form and mixed by dewatering system operators into a solution prior to treating a mud system. Also, because the dry polymer is added to a liquid, an aging process is required to activate the dry polymers. Additionally, these polymers tend to be hygroscopic, and as such, have a limited shelf life. Thus, when housed in outdoor storage facilities, such as typically occurs in current commercial drilling operations, the hygroscopic polymers take on water, thereby decreasing their effective life. Also, the polymers in current commercial systems are typically exposed to wide temperature variations, further resulting in decreased effective life. Due to the need of polymer solution aging, batch mixing, and the limited shelf life in current commercial systems, management of dry flocculant dewatering systems is costly and resource dependent.
In response to the increased use of water-based drilling fluids, many companies now manufacture invert emulsion liquid flocculants and coagulants that provide increased activity and shelf life. However, due to their nanoemulsion formulation, these products require high energy for emulsion breaking and activation. Also, the liquid flocculants and coagulants still experience decreased shelf life when exposed to moisture and wide temperature variation. Thus, the liquid flocculants and coagulants do not always work effectively in current commercial systems.
Accordingly, there exists a need for a self-contained, climatized, and automated dewatering system.